In eighteenth and nineteenth century England, the strongest versions of Porter were known as Stout Porter; over the years, this was shortened to simply Stout.

The most famous porter in the world is undoubtedly Guinness, one of the few internationally recognizable dark beers. Guinness were among the first to add roasted barley to a dark, strong porter, which quickly became a hallmark of the style. During World War I, when roasted malts were not available in England, Ireland came to dominate the Stout market and became closely associated with the style.

The worldwide popularity of Guinness led to a number of regional stout styles which emerged throughout the world, from the strong, dark Russian Imperial Stout to the fruity, bottom-fermented Tropical Stout. And with the emergence of the craft beer movement in the United States and England, this dark, roasted beer, so different from the popular golden lagers, became a signature beer for many microbreweries and brewpubs.

The stouts which have grown up around Guinness and its Irish rivals are generally known as Dry Stout, Irish Stout, or Dry Irish Stout. This is a relatively low-alcohol, light-bodied, dark but easy-drinking session beer. Dry Stouts have a significant roasted flavor from unmalted roasted barley and a creamy character, often enhanced by special dispensing techniques such as stout faucets or nitrogen.

The best-known Dry Stout is Guinness Draught; other commercial examples include Murphy's Irish Stout and Beamish Irish Stout. Although Michael Jackson suggests that the relatively low original gravities of Murphy's and Beamish make them more akin to porter.

Milk Stout is similar to Dry Stout, but sweet rather than dry. Sometimes called Sweet Stout or Cream Stout, Milk Stout is usually sweetened not by low attenuation but by the addition of unfermentable sugars, usually lactose (derived from milk). Due to UK and EU regulations, the traditional name, "Milk Stout", can no longer be used by English brewers but is still used in many American commercial examples.

Oatmeal stout was originally an English seasonal variant of sweet stout that is usually less sweet than the original, and relies on oatmeal for body and complexity rather than lactose for body and sweetness. As a general rule, pale, caramel and dark roasted malts and grains are used along with between 5 and 10 percent of oatmeal to enhance fullness of body and complexity of flavor. The ale is brown to black in color.

American stout is a style that was born in the American microbrewery movement. It generally has bolder roasted malt flavors and hopping than other traditional stouts (other than Imperial Stouts), and brewed with primarily American hops, such as cascade and Willamette.

The Guinness brewed for export was traditionally brewed to a higher gravity, resulting in a higher alcohol, stronger flavored beer. Until recently, this was the only kind of Stout known in many parts of the world, and became the standard style of bottled or canned stout until the introduction of nitrogen widgets and other new dispensing technology. Beers brewed to this standard are known as Export Stout, Foreign Extra Stout, or Foreign Export Stout. They are sometimes brewed with brettanomyces to create an extra strong flavor.

Tropical stout is the term usually applied to the sweet, high-gravity stouts often brewed in the Carribbean and elsewhere. These stouts were often brewed as domestic versions of the Foreign Extra Stouts that were available for import in those countries, but modified to fit in with existing Carribbean brewing traditions. Unlike any other style of stout, Tropical Stouts are often brewed with bottom-fermenting (lager) yeast.

Some stout brewers brewed special dark, strong beers for export to the Baltic states, which became known as Russian Imperial Stout. These are strong beers, 8% ABV or more, with correspondingly more malt and hop flavor and bitterness. The Russian Imperial Stout is the original source of the term "Imperial", now used generically to indicate any beer brewed with higher than traditional original gravity and bitterness, as for example an Imperial IPA.

Home and craft brewers now call almost any large, strong stout an Imperial Stout. These beers are united by high alcohol content and enormous flavor profiles, usually with some noticeable alcohol and (especially in American versions) significant bitterness. However, many of them bear little resemblance to the historical Russian or Baltic stouts and they are probably better thought of as their own category.

Oyster Stout, also known as Love Stout, is a stout brewed with either whole oysters, added at the end of the boil, or oyster shells. This style, while never common, was developed by English brewers in the early twentieth century and has been picked up recently by some "extreme" American brewers; it is one of the very few defined meat-based beer styles. It may have derived from an earlier practice of referring to a stout meant to be served with oysters as an "Oyster Stout".

When an oyster is simply added to a glass of ordinary stout at serving time, this is known as an Oyster Shooter.

Breakfast stout is brewed with coffee. Sometimes this is known as Coffee Stout, although this name is also sometimes used for stouts with a coffee flavor from roasted barley, rather than actual coffee.

Recently, some Belgian brewers, and some American brewers of Belgian-style beers, have begun brewing beers inspired by English and Irish stouts. These Belgian Stouts often feature the roasted flavor of a traditional dry stout combined with a flavorful Belgian yeast.

Stouts such as Guinness are well known for having an especially creamy head. This is achieved by using a mix of CO2 and NO2 in the beer. Nitrogen doesn't dissolve well in beer, and so when it is poured in to the glass (and therefore relieving the pressure that kept the nitrogen in solution in the keg) it comes out of solution much quicker than CO2 would. Since the molecules are smaller, the bubbles are smaller, creating the creaminess that is well known. A simpler way of achieving this is by installing a restricter nozzle onto the tap, which forces the beer through a plate with holes, creating a similar but not identical effect.

In the UK, a Beer engine is used to dispense a lot of stouts, which lends them a smooth texture.

Stouts are best served slightly warmer than traditional ales, somewhere in the 6-8C mark. This higher temperature brings out the roast and chocolate flavours that dominate most stouts and encourage the 'warmness' that tends to come with the higher alcohol volumes in stouts such as Russian imperial.

Mouthfeel: Medium-light to medium-full body, with a creamy character. Low to moderate carbonation. For the high hop bitterness and significant proportion of dark grains present, this beer is remarkably smooth. The perception of body can be affected by the overall gravity with smaller beers being lighter in body. May have a light astringency from the roasted grains, although harshness is undesirable.

History: The style evolved from attempts to capitalize on the success of London porters, but originally reflected a fuller, creamier, more "stout" body and strength. When a brewery offered a stout and a porter, the stout was always the stronger beer (it was originally called a "Stout Porter"). Modern versions are brewed from a lower OG and no longer reflect a higher strength than porters.

Comments: This is the draught version of what is otherwise known as Irish stout or Irish dry stout. Bottled versions are typically brewed from a significantly higher OG and may be designated as foreign extra stouts (if sufficiently strong). While most commercial versions rely primarily on roasted barley as the dark grain, others use chocolate malt, black malt or combinations of the three. The level of bitterness is somewhat variable, as is the roasted character and the dryness of the finish; allow for interpretation by brewers.

Ingredients: The dryness comes from the use of roasted unmalted barley in addition to pale malt, moderate to high hop bitterness, and good attenuation. Flaked unmalted barley may also be used to add creaminess. A small percentage (perhaps 3%) of soured beer is sometimes added for complexity (generally by Guinness only). Water typically has moderate carbonate hardness, although high levels will not give the classic dry finish.

History: An English style of stout. Historically known as "Milk" or "Cream" stouts, legally this designation is no longer permitted in England (but is acceptable elsewhere). The "milk" name is derived from the use of lactose, or milk sugar, as a sweetener.

Comments: Gravities are low in England, higher in exported and US products. Variations exist, with the level of residual sweetness, the intensity of the roast character, and the balance between the two being the variables most subject to interpretation.

Ingredients: The sweetness in most Sweet Stouts comes from a lower bitterness level than dry stouts and a high percentage of unfermentable dextrins. Lactose, an unfermentable sugar, is frequently added to provide additional residual sweetness. Base of pale malt, and may use roasted barley, black malt, chocolate malt, crystal malt, and adjuncts such as maize or treacle. High carbonate water is common.

Aroma: Mild roasted grain aromas, often with a coffee-like character. A light sweetness can imply a coffee-and-cream impression. Fruitiness should be low to medium. Diacetyl medium-low to none. Hop aroma low to none (UK varieties most common). A light oatmeal aroma is optional.

Appearance: Medium brown to black in color. Thick, creamy, persistent tan- to brown-colored head. Can be opaque (if not, it should be clear).

Flavor: Mild roasted grain aromas, often with a coffee-like character. A light sweetness can imply a coffee-and-cream impression. Fruitiness should be low to medium. Diacetyl medium-low to none. Hop aroma low to none (UK varieties most common). A light oatmeal aroma is optional.

Mouthfeel: Medium-full to full body, smooth, silky, sometimes an almost oily slickness from the oatmeal. Creamy. Medium to medium-high carbonation.

Overall Impression: Mild roasted grain aromas, often with a coffee-like character. A light sweetness can imply a coffee-and-cream impression. Fruitiness should be low to medium. Diacetyl medium-low to none. Hop aroma low to none (UK varieties most common). A light oatmeal aroma is optional.

History: An English seasonal variant of sweet stout that is usually less sweet than the original, and relies on oatmeal for body and complexity rather than lactose for body and sweetness.

Comments: Generally between sweet and dry stouts in sweetness. Variations exist, from fairly sweet to quite dry. The level of bitterness also varies, as does the oatmeal impression. Light use of oatmeal may give a certain silkiness of body and richness of flavor, while heavy use of oatmeal can be fairly intense in flavor with an almost oily mouthfeel. When judging, allow for differences in interpretation.

Ingredients: Pale, caramel and dark roasted malts and grains. Oatmeal (5-10%+) used to enhance fullness of body and complexity of flavor. Hops primarily for bittering. Ale yeast. Water source should have some carbonate hardness.

Aroma: Roasted grain aromas moderate to high, and can have coffee, chocolate and/or lightly burnt notes. Fruitiness medium to high. Some versions may have a sweet aroma, or molasses, licorice, dried fruit, and/or vinous aromatics. Stronger versions can have the aroma of alcohol. Hop aroma low to none. Diacetyl low to none.

Appearance: Very deep brown to black in color. Clarity usually obscured by deep color (if not opaque, should be clear). Large tan to brown head with good retention.

Flavor: Roasted grain aromas moderate to high, and can have coffee, chocolate and/or lightly burnt notes. Fruitiness medium to high. Some versions may have a sweet aroma, or molasses, licorice, dried fruit, and/or vinous aromatics. Stronger versions can have the aroma of alcohol. Hop aroma low to none. Diacetyl low to none.

Mouthfeel: Medium-full to full body, often with a smooth, creamy character. May give a warming impression from alcohol presence. Moderate to moderately-high carbonation.

Overall Impression: Roasted grain aromas moderate to high, and can have coffee, chocolate and/or lightly burnt notes. Fruitiness medium to high. Some versions may have a sweet aroma, or molasses, licorice, dried fruit, and/or vinous aromatics. Stronger versions can have the aroma of alcohol. Hop aroma low to none. Diacetyl low to none.

History: Originally high-gravity stouts brewed for tropical markets (and hence, sometimes known as "Tropical Stouts"). Some bottled export (i.e. stronger) versions of dry or sweet stout also fit this profile. Guinness Foreign Extra Stout has been made since the early 1800s.

Comments: A rather broad class of stouts, these can be either fruity and sweet, dry and bitter, or even tinged with Brettanomyces (e.g., Guinness Foreign Extra Stout; this type of beer is best entered as a Specialty or Experimental beer). Think of the style as either a scaled-up dry and/or sweet stout, or a scaled-down Imperial stout without the late hops. Highly bitter and hoppy versions are best entered as American-style Stouts.

Ingredients: Similar to dry or sweet stout, but with more gravity. Pale and dark roasted malts and grains. Hops mostly for bitterness. May use adjuncts and sugar to boost gravity. Ale yeast (although some tropical stouts are brewed with lager yeast).

Aroma: Moderate to strong aroma of roasted malts, often having a roasted coffee or dark chocolate quality. Burnt or charcoal aromas are low to none. Medium to very low hop aroma, often with a citrusy or resiny American hop character. Esters are optional, but can be present up to medium intensity. Light alcohol-derived aromatics are also optional. No diacetyl.

Appearance: Generally a jet black color, although some may appear very dark brown. Large, persistent head of light tan to light brown in color. Usually opaque.

Flavor: Moderate to strong aroma of roasted malts, often having a roasted coffee or dark chocolate quality. Burnt or charcoal aromas are low to none. Medium to very low hop aroma, often with a citrusy or resiny American hop character. Esters are optional, but can be present up to medium intensity. Light alcohol-derived aromatics are also optional. No diacetyl.

Mouthfeel: Medium to full body. Can be somewhat creamy, particularly if a small amount of oats have been used to enhance mouthfeel. Can have a bit of roast-derived astringency, but this character should not be excessive. Medium-high to high carbonation. Light to moderately strong alcohol warmth, but smooth and not excessively hot.

Overall Impression: Moderate to strong aroma of roasted malts, often having a roasted coffee or dark chocolate quality. Burnt or charcoal aromas are low to none. Medium to very low hop aroma, often with a citrusy or resiny American hop character. Esters are optional, but can be present up to medium intensity. Light alcohol-derived aromatics are also optional. No diacetyl.

Ingredients: Common American base malts and yeast. Varied use of dark and roasted malts, as well as caramel-type malts. Adjuncts such as oatmeal may be present in low quantities. American hop varieties.

Aroma: Rich and complex, with variable amounts of roasted grains, maltiness, fruity esters, hops, and alcohol. The roasted malt character can take on coffee, dark chocolate, or slightly burnt tones and can be light to moderately strong. The malt aroma can be subtle to rich and barleywine-like, depending on the gravity and grain bill. May optionally show a slight specialty malt character (e.g., caramel), but this should only add complexity and not dominate. Fruity esters may be low to moderately strong, and may take on a complex, dark fruit (e.g., plums, prunes, raisins) character. Hop aroma can be very low to quite aggressive, and may contain any hop variety. An alcohol character may be present, but shouldn't be sharp, hot or solventy. Aged versions may have a slight vinous or port-like quality, but shouldn't be sour. No diacetyl. The balance can vary with any of the aroma elements taking center stage. Not all possible aromas described need be present; many interpretations are possible. Aging affects the intensity, balance and smoothness of aromatics.

Appearance: Color may range from very dark reddish-brown to jet black. Opaque. Deep tan to dark brown head. Generally has a well-formed head, although head retention may be low to moderate. High alcohol and viscosity may be visible in "legs" when beer is swirled in a glass.

Flavor: Rich and complex, with variable amounts of roasted grains, maltiness, fruity esters, hops, and alcohol. The roasted malt character can take on coffee, dark chocolate, or slightly burnt tones and can be light to moderately strong. The malt aroma can be subtle to rich and barleywine-like, depending on the gravity and grain bill. May optionally show a slight specialty malt character (e.g., caramel), but this should only add complexity and not dominate. Fruity esters may be low to moderately strong, and may take on a complex, dark fruit (e.g., plums, prunes, raisins) character. Hop aroma can be very low to quite aggressive, and may contain any hop variety. An alcohol character may be present, but shouldn't be sharp, hot or solventy. Aged versions may have a slight vinous or port-like quality, but shouldn't be sour. No diacetyl. The balance can vary with any of the aroma elements taking center stage. Not all possible aromas described need be present; many interpretations are possible. Aging affects the intensity, balance and smoothness of aromatics.

Mouthfeel: Full to very full-bodied and chewy, with a velvety, luscious texture (although the body may decline with long conditioning). Gentle smooth warmth from alcohol should be present and noticeable. Should not be syrupy and under-attenuated. Carbonation may be low to moderate, depending on age and conditioning.

Overall Impression: Rich and complex, with variable amounts of roasted grains, maltiness, fruity esters, hops, and alcohol. The roasted malt character can take on coffee, dark chocolate, or slightly burnt tones and can be light to moderately strong. The malt aroma can be subtle to rich and barleywine-like, depending on the gravity and grain bill. May optionally show a slight specialty malt character (e.g., caramel), but this should only add complexity and not dominate. Fruity esters may be low to moderately strong, and may take on a complex, dark fruit (e.g., plums, prunes, raisins) character. Hop aroma can be very low to quite aggressive, and may contain any hop variety. An alcohol character may be present, but shouldn't be sharp, hot or solventy. Aged versions may have a slight vinous or port-like quality, but shouldn't be sour. No diacetyl. The balance can vary with any of the aroma elements taking center stage. Not all possible aromas described need be present; many interpretations are possible. Aging affects the intensity, balance and smoothness of aromatics.

History: Brewed to high gravity and hopping level in England for export to the Baltic States and Russia. Said to be popular with the Russian Imperial Court. Today is even more popular with American craft brewers, who have extended the style with unique American characteristics.

Comments: Variations exist, with English and American interpretations (predictably, the American versions have more bitterness, roasted character, and finishing hops, while the English varieties reflect a more complex specialty malt character and a more forward ester profile). The wide range of allowable characteristics allow for maximum brewer creativity.

Ingredients: Well-modified pale malt, with generous quantities of roasted malts and/or grain. May have a complex grain bill using virtually any variety of malt. Any type of hops may be used. Alkaline water balances the abundance of acidic roasted grain in the grist. American or English ale yeast.

Dry stouts have an initial malt and light caramel flavor profile with a distinctive dry-roasted bitterness in the finish. Dry stouts achieve a dry-roasted character through the use of roasted barley. The emphasis of coffee-like roasted barley and a moderate degree of roasted malt aromas define much of the character. Some slight acidity may be perceived but is not necessary. Hop aroma and flavor should not be perceived. Dry stouts have medium-light to medium body. Fruity esters are minimal and overshadowed by malt, high hop bitterness, and roasted barley character. Diacetyl (butterscotch) should be very low or not perceived. Head retention and rich character should be part of its visual character.

As with classic dry stouts, foreign style stouts have an initial malt sweetness and caramel flavor with a distinctive dry roasted bitterness in the finish. Coffee-like roasted barley and roasted malt aromas are prominent. Some slight acidity is permissible and a medium to full bodied mouthfeel is appropriate. Bitterness may be high but the perception is often compromised by malt sweetness. Hop aroma and flavor should not be perceived. The perception of fruity esters is low. Diacetyl (butterscotch) should be negligible or not perceived. Head retention is excellent.

Initial low to medium malt sweetness with a degree of caramel, chocolate and/or roasted coffee flavor with a distinctive dry-roasted bitterness in the finish. Coffee-like roasted barley and roasted malt aromas are prominent. Some slight roasted malt acidity is permissible and a medium- to full-bodied mouthfeel is appropriate. Hop bitterness may be moderate to high. Hop aroma and flavor is moderate to high often with American citrus-type and/or resiny hop character. The perception of fruity esters is low. Roasted malt/barley astringency may be low but not excessive. Diacetyl (butterscotch) should be negligible or not perceived. Head retention is excellent.

Sweet stouts, also referred to as cream stouts, have less roasted bitter flavor and a full bodied mouthfeel. The style can be given more body with milk sugar (lactose) before bottling. Malt sweetness, chocolate, and caramel flavor should dominate the flavor profile and contribute to the aroma. Hops should balance sweetness without contributing apparent flavor or aroma.

Oatmeal stouts include oatmeal in their grist, resulting in a pleasant, full flavor and a smooth profile that is rich without being grainy. A roasted malt character which is caramel-like and chocolate-like should be evident - smooth and not bitter. Coffee-like roasted barley and roasted malt aromas (chocolate and nut-like) are prominent. Bitterness is moderate, not high. Hop flavor and aroma are optional but should not overpower the overall balance if present. This is a medium to full bodied beer, with minimal fruity esters.

Dark copper to very dark brown, British-style imperial stouts typically have high alcohol content. The extremely rich malty flavor (often characterized as toffee-like or caramel-like) and aroma are balanced with medium hopping and high fruity-ester characteristics. Bitterness should be moderate and balanced with sweet malt character. The bitterness may be higher in the darker versions. Roasted malt astringency is very low or absent. Bitterness should not overwhelm the overall character. Hop aroma can be subtle to moderately hop-floral, -citrus or -herbal. Diacetyl (butterscotch) levels should be absent.

Black to very black, American-style imperial stouts typically have a high alcohol content. Generally characterized as very robust. The extremely rich malty flavor and aroma are balanced with assertive hopping and fruity-ester characteristics. Bitterness should be moderately high to very high and balanced with full sweet malt character. Roasted malt astringency and bitterness can be moderately perceived but should not overwhelm the overall character. Hop aroma is usually moderately-high to overwhelmingly hop-floral, -citrus or -herbal. Diacetyl (butterscotch) levels should be absent.